Back to EveryPatent.com
| United States Patent |
5,534,443
|
|
Ohtagaki
, et al.
|
July 9, 1996
|
Method of manufacturing a solid state imaging device
Abstract
The method of manufacturing a solid state imaging device of the invention
comprises a step of adding carboxylate as a dyeing assistant auxiliary to
the aqueous dyestuff solution when forming dyeing layers of acrylic-based
resin on a semiconductor substrate on which a solid state imaging element
is formed. Therefore this invention provides a solid state imaging device
with a color filter which is dyed densely, is flat, thin, and excellent in
spectral characteristics. A transparent planarization resin layer (the
material is e.g. acrylic) is formed on a semiconductor substrate, and a
shading layer and planarization resin layer are successively formed
thereon. A synthetic resin is prepared and added photosensitizer of diazo
compound. On the above-mentioned planarization resin layer, the layer of
the synthetic resin is coated to be 0.2 to 0.8 .mu.m thick, for example,
by a spin coat method. Then the synthetic resin is selectively exposed
with a stepper, and developed to form patterns of a color filter. Then,
the resin with the pattern is dyed to be a cyan layer. In the step,
ammonium acetate and a urea compound are added to the aqueous dyestuff
solution.
| Inventors:
|
Ohtagaki; Tomoko (Kyoto, JP);
Sano; Yoshikazu (Osaka, JP)
|
| Assignee:
|
Matsushita Electronics Corporation (Osaka, JP)
|
| Appl. No.:
|
408974 |
| Filed:
|
March 23, 1995 |
Foreign Application Priority Data
| Current U.S. Class: |
438/70; 257/E31.121; 257/E31.122; 257/E31.128 |
| Intern'l Class: |
H01L 031/18 |
| Field of Search: |
437/2,3,4,5,127,905
148/DIG. 99
|
References Cited
U.S. Patent Documents
| 3963495 | Jun., 1976 | Kato et al. | 430/232.
|
| 4052379 | Oct., 1977 | Gourley | 534/768.
|
| 5404005 | Apr., 1995 | Shimomura et al. | 250/208.
|
| Foreign Patent Documents |
| 130102A | May., 1989 | JP.
| |
Primary Examiner: Thomas; Tom
Assistant Examiner: Picardat; Kevin M.
Attorney, Agent or Firm: Fish & Richardson
Claims
What is claimed is:
1. A method of manufacturing a solid state imaging device comprising
forming dyeing layers of acrylic-based resin on a semiconductor substrate
on which a solid state imaging element is formed and adding carboxylate
and a urea compound as dyeing assistant auxiliaries in an aqueous dyestuff
solution in the step of forming the dyeing layers of acrylic-based resin
on the semiconductor substrate, wherein the urea is added to the aqueous
dyestuff solution in an amount of from 0.1 to 10 weight percent based on
the amount of the aqueous dyestuff solution.
2. The method of manufacturing a solid state imaging device according to
claim 1, wherein the carboxylate is at least one salt selected from the
group consisting of ammonium carboxylate and alkali metal carboxylate.
3. The method of manufacturing a solid state imaging device according to
claim 2, wherein the alkali metal carboxylate is selected from the group
consisting of sodium carboxylate and potassium carboxylate.
4. The method of manufacturing a solid state imaging device according to
claim 1, wherein the carboxylate is at least one carboxylic acid salt
selected from the group consisting of formic acid, acetic acid, propionic
acid, n-butyric acid, isobutyric acid, valeric acid, trimethyl acetic
acid, acrylic acid, and methacrylic acid.
5. The method of manufacturing a solid state imaging device according to
claim 1, wherein the amount of carboxylate added is from 0.05 to 2 weight
percent based on the amount of aqueous dyestuff solution.
6. The method of manufacturing a solid state imaging device according to
claim 1, wherein the urea compound is C.sub.q H.sub.r O.sub.s N.sub.t,
where q is from 1 to 5, r is from 4 to 10, s is 1, and t is 2.
7. The method of manufacturing a solid state imaging device according to
claim 1, wherein the urea compound is ethyleneurea.
8. The method of manufacturing a solid state imaging device according to
claim 1, wherein planarization resin layers, a shading layer, and
multicolor dyeing layers are formed successively on the semiconductor
substrate on which said solid state imaging element is formed.
9. The method of manufacturing a solid state imaging device according to
claim 8, wherein the multicolor dyeing layers is at least one color
selected from the group consisting of yellow, cyan, magenta, and green.
10. The method of manufacturing a solid state imaging device according to
claim 8, wherein the multicolor dyeing layers is at least one color
selected from the group consisting of red, blue, and green.
11. The method of manufacturing a solid state imaging device according to
claim 1, wherein planarization resin layers and a shading layer comprising
monocolor dyeing layer are formed successively on the semiconductor
substrate on which said solid state imaging element is formed.
12. The method of manufacturing a solid state imaging device according to
claim 11, wherein the monocolor dyeing layer is black.
13. The method of manufacturing a solid state imaging device according to
claim 1, wherein the step of forming the dyeing layers comprises:
forming an acrylic-based resin layer (A), dyeing the acrylic-based resin
layer (A) a color, and fixing the dye;
forming another acrylic-based resin layer (B), dyeing the acrylic-based
resin layer (B) another color, and fixing the dye.
14. The method of manufacturing a solid state imaging device according to
claim 13, wherein the acrylic-based resin layer (A) and the other
acrylic-based resin layer (B) are adjacent or partly overlapping each
other from a cross-sectional view.
Description
FIELD OF THE INVENTION
This invention relates to a method of manufacturing a solid state imaging
device comprising two types, namely, a charge coupled device (hereinafter
abbreviated as CCD) and a metal oxide semiconductor (hereinafter
abbreviated as MOS). More specifically, this invention relates to a method
of dyeing layers on a semiconductor substrate on which a solid state
imaging element is formed.
BACKGROUND OF THE INVENTION
Due to the recent trend toward miniaturizing solid state imaging devices
and improving the quality of pixels, several problems have been noted. For
instance, sensitivity deteriorates because of a decrease in the
photo-conversion area, and the smear characteristics degrade under the
influence of oblique rays, since the space between adjacent
photo-conversion parts has been reduced. Smear characteristic is a
phenomenon that occurs when oblique rays from a photodiode generate free
electrons at the bottom of a solid state imaging device and are captured
by the solid state imaging device. In order to solve such problems, solid
state imaging devices for general use are equipped with microlens layers
on the photo-conversion part, or equipped with shading layers. The
photo-conversion area should be decreased in order to improve the quality
of miniaturizing CCD's pixels. Thus it may be necessary to miniaturize a
photo-conversion body, which will shorten the focal length. As a result, a
filter is required to be thinner so that it is easier to condense rays
with a microlens. Furthermore, it is necessary to raise the
photo-absorption rate of the shading layer in order to improve the smear
characteristics, since the oblique rays influence on the smear
characteristics.
As a method of manufacturing color filters, Japanese Laid Open Patent
Application No. (Tokkai-Hei) 1-130102 discloses the use of
m-nitrobenzenesulfonate and/or urea as dyeing assistant auxiliaries. A
dyeing assistant auxiliary is used to promote dyeing.
However, the conventional method of manufacturing color solid state imaging
devices causes problems such as surface roughness, which occurs when the
surface of a filter becomes slightly rough or uneven. Desirable spectral
characteristics cannot be easily obtained due to surface roughness.
SUMMARY OF THE INVENTION
It is an object of this invention to solve the above-mentioned problems by
providing a method of manufacturing a solid state imaging device with a
color filter which is easily dyed, has a flat surface and desirable
spectral characteristics.
In order to accomplish these and other objects and advantages, the method
of manufacturing a solid state imaging device of the invention comprises
adding carboxylate as a dyeing assistant auxiliary to a solution of
aqueous dyestuffs when forming dyeing layers of acrylic-based resin on a
semiconductor substrate on which a solid state imaging element is formed.
It is preferable in the invention that the carboxylate is at least one salt
selected from the group consisting of ammonium carboxylate and alkali
metal carboxylate.
It is also preferable in the invention that the alkali metal carboxylate is
at least one salt selected from the group consisting of sodium carboxylate
and potassium carboxylate.
It is further preferable in the invention that the alkali metal carboxylate
is at least one salt of carboxylic acid salt selected from the group
consisting of formic acid, acetic acid, propionic acid, n-butyric acid,
isobutyric acid, valeric acid, trimethyl acetic acid, acryl acid, and
methacryl acid.
It is preferable in the invention that the carboxylate is added in an
amount of from 0.05 to 2 weight percent (hereinafter wt. %) based on
amount of aqueous dyestuff solution.
It is also preferable in the invention that a urea compound is also added
to the aqueous dyestuff solution in an amount of 0.1 to 10 wt. % based on
amount of aqueous dyestuff solution.
It is further preferable in the invention that the urea compound is C.sub.q
H.sub.r O.sub.s N.sub.t where q is from 1 to 5, r is from 4 to 10, s is 1,
and t is 2.
It is preferable in the invention that the urea compound is ethyleneurea
(2-imidazolidone).
It is preferable in the invention that the planarization resin layers and
the shading layer are formed on the semiconductor substrate on which the
solid state imaging element is formed and multicolor dyeing layers are
formed thereon. A planarization resin layer passes outside lights
efficiently to the surface of a photoconversion area. A shading layer
blocks lights which come through adjacent lenses and other dyeing layers.
It is preferable in the invention that the color of the multicolor dyeing
layers are at least one selected from the group consisting of yellow,
cyan, magenta, and green.
It is preferable in the invention that the color of the multicolor dyeing
layers are at least one selected from the group consisting of red, blue,
and green.
It is preferable in the invention that the planarization resin layers and
the shading layer are formed successively on the semiconductor substrate
on which the solid state imaging element is formed, and the shading layer
consists of a monocolor dyeing layer.
It is preferable in the invention that the color of the monocolor dyeing
layer is black.
It is preferable in the invention that the dyeing layers are manufactured
as follows:
forming an acrylic-based resin layer (A), dyeing the acrylic-based resin
layer (A) a color, and fixing the dye;
forming a second acrylic-based resin layer (B), dyeing the acrylic-based
resin layer (B) another color, and fixing the dye.
It is preferable in the invention that the acrylic-based resin layer (A)
and the acrylic-based resin layer (B) are adjacent or partly overlapping
each other from a cross-sectional view.
As described above, a solid state imaging device of the invention can be
employed for CCD and MOS, both of which are well known to any person
skilled in the art.
The method of manufacturing a solid state imaging device of the invention
comprises adding carboxylate as a dyeing assistant auxiliary to the
aqueous dyestuff solution when forming dyeing layers of acrylic-based
resin on a semiconductor substrate on which a solid state imaging element
is formed. Therefore this invention provides a solid state imaging device
with a color filter which is dyed densely, is flat, thin, and excellent in
spectral characteristics. Moreover, the method of the invention can
increase yield in manufacturing a solid state imaging device, since
particles, which are generated from aggregation of additives such as
dyestuffs, decrease during a dye bath.
Furthermore, this invention provides preferable spectra by using thin
films, thus provides thinner color filter layer (from a photo-conversion
part to a microlens). Therefore the focal length of the lens becomes
shorter, and the condensing rate can be improved. As a result, sensitivity
of the photo-conversion part will be improved even if the image sensing
scene gets dark and the optical diaphragm is open. In addition, smear
characteristics will be improved by raising the photo-absorption rate of
the shading layer.
According to a preferable embodiment of the invention the carboxylate is at
least one salt selected from the group consisting of ammonium carboxylate
and alkali metal carboxylate. Therefore, it is possible not only to dye
more densely and avoid surface roughness of filters, but also to decrease
particles which are generated from aggregation of additives such as
dyestuff in the aqueous dyestuff solution.
According to a preferable embodiment of the invention the alkali metal
carboxylate is at least one salt selected from the group consisting of
sodium carboxylate and potassium carboxylate. Therefore, it is possible
not only to dye more densely and avoid surface roughness of filters, but
also to decrease particles which are generated from aggregation of
additives such as dyestuff in the aqueous dyestuff solution.
It is also preferable in the invention that the carboxylate is at least one
carboxylic acid salt selected from the group consisting of formic acid,
acetic acid, propionic acid, n-butyric acid, isobutyric acid, valeric
acid, trimethyl acetic acid, acryl acid, and methacryl acid. As a result,
it is possible to dye more densely and avoid surface roughness of filters,
as well as to decrease particles which are generated from aggregation of
additives such as dyestuff in the aqueous dyestuff solution.
It is possible to carry out the above-mentioned step more efficiently if
the carboxylate is added in the amount of from 0.05 to 2 wt. %. If the
amount of the caboxylate is less than 0.05 wt. %, it will be more
difficult to dye densely. Moreover, it will be more difficult to control
particles which are generated by aggregation of additives such as
dyestuffs in the aqueous dyestuff solution. It is also difficult to
prevent surface roughness of the filter. Adding carboxylate in an amount
of over 2 wt. % does not improve the quality so much, while it raises the
production cost.
It is further preferable in the invention to add a urea compound in an
amount of from 0.1 to 10 wt. % to the above-mentioned aqueous dyestuff
solution. Therefore it is possible to dye more densely in some
predetermined dyestuffs and to avoid surface roughness of filters, as well
as to decrease particles which are generated from aggregation of additives
such as dyestuffs in aqueous dyestuff solution. As the urea compound,
C.sub.q H.sub.r O.sub.s N.sub.t is preferable where q is from 1 to 5, r is
from 4 to 10, s is 1, and t is 2. Ethyleneurea (2-imidazolidone) is
particularly preferable.
It is possible to form planarization resin layers and a shading layer on a
semiconductor substrate on which a solid state imaging element is formed,
and multicolor dyeing layers (a color filter layer) are formed thereon
successively. In this embodiment, the shading layer is dyed black, and the
color filter is dyed multicolor. The multicolor dyeing layers are dyed at
least one color selected from the group consisting of yellow, cyan,
megenta, and green. Or the multicolor dyeing layers are dyed at least one
color selected from the group consisting of red, blue, and green. Solid
state imaging devices with color filters are employed for video cameras
for private use and others.
In another embodiment, it is also possible to form a planarization resin
layer, a shading layer comprising a monocolor dyeing layer (black)
successively on a semiconductor substrate on which a solid state imaging
element is formed. Solid state imaging devices which are manufactured in
this embodiment can be employed for monocolor (white and black) cameras
for various uses such as viewing, medical, and business.
In the invention, it is possible to form a color filter efficiently
according to the following steps:
forming an acrylic-based resin layer (A), dyeing the aclylic-based layer
(A) a predetermined color, and fixing the dye;
forming another acrylic-based resin layer (B), dyeing the acrylic-based
resin layer (B) another color, and fixing the dye.
It is preferable that the acrylic-based resin layer (A) and the
acrylic-based resin layer (B) are adjacent or partly overlapping each
other from a cross-sectional view.
As described above, the method of manufacturing a solid state imaging
device of the invention comprises adding carboxylate as a dyeing assistant
auxiliary to the aqueous dyestuff solution when forming dyeing layers of
acrylic-based resin on a semiconductor substrate on which a solid state
imaging element is formed. Therefore this invention provides a solid state
imaging device a with color filter which is dyed densely, is flat, thin,
and excellent in spectral characteristics. Moreover, the method of the
invention can improve yield in manufacturing a solid state imaging device,
since particles which are generated from aggregation of additives such as
dyestuffs decrease.
Furthermore, this invention provides preferable spectrum by using thin
film, thus provides thinner color filter layer which comprises from
photo-conversion part to microlenses. Therefore focal length of the lens
becomes shorter and the condensing rate can be improved. As a result,
sensitivity of the photo-conversion part will be improved even if the
image sensing scene gets dark and the optical diaphragm is open. In
addition, smear characteristics will be improved by raising
photo-absorption rate of the shading layer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1(a) to FIG. 1(f) are cross-sectional views showing the method of
manufacturing the color solid state imaging device of Example 1 of this
invention.
FIG. 2 indicates the relation between the amount of additives (ammonium
acetate and urea compound) and the absorbance of the filter of Example 1
of this invention.
FIG. 3 indicates the spectral characteristics of the color filter of
Example 1 of the invention.
FIG. 4 indicates spectral characteristics of the colors of the color
filters of Example 1 of the invention.
FIG. 5(a) to FIG. 5(f) are cross-sectional views showing the method of
manufacturing the solid state imaging device of Example 2 of this
invention.
FIG. 6 indicates the relation between the amount of additives (sodium
acetate and urea compound) and the absorbance of the filters of Example 2
of this invention.
FIG. 7 indicates the absorbance of red filter of Example 2 of this
invention when varying amounts of sodium acetate and urea compound
(ethyleneurea) are added to the aqueous dyestuff solution.
FIG. 8 indicates the spectral characteristics of the color filters of
Example 2 of the invention.
FIG. 9 indicates the spectral characteristics of the colors of the color
filter of Example 1 of the invention.
FIG. 10(a) to FIG. 10(d) are cross-sectional views showing the method of
manufacturing the solid state imaging device of Example 3 of this
invention.
FIG. 11 indicates the relation between the amount of additive (potassium
acetate) and the absorbance of the filters of Example 3 of this invention.
FIG. 12 indicates absorbance of the black filter of Example 3 of this
invention when varying amounts of potassium acetate and urea compound
(ethyleneurea) are added to the aqueous dyestuff solution.
FIG. 13 indicates the spectral characteristics of the shading filter of
Example 3 of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The following is a method of manufacturing a solid state imaging device of
one embodiment of the invention.
A planarization resin layer made of a transparent material such as acrylic
resin is formed on a wafer on which a solid state imaging element is
formed, and forming a shading layer and another planarization resin layer
successively.
The planarization resin layer is coated with a dyeable material layer (a
layer to be dyed) which consists of synthetic resin, exposing selectively,
and developing to form a predetermined pattern.
The above-mentioned pattern is dyed in a aqueous dyestuff solution of
predetermingly adjusted yellow dye in order to form a yellow layer.
The dye is fixed with adhering agent such as tannic acid aqueous solution
and potassium antimonyl-tartrate solution to prevent decolor and mixture
of colors.
The layers are coated with another dyeable material layer which consists of
synthetic resin, and forming a cyan layer in the same manner of the yellow
layer.
A magenta layer is formed according to the above-mentioned manner.
A green layer is formed where the yellow layer and the cyan layer are
overlapping each other.
The color filter layer is coated with a planarization layer of transparent
materials such as acrylic resin layer in order to flatten the surface of
the color filters.
The layers are coated with a lens material resin and the material is
exposed selectively, and developed to be the lens material resin layer
which is almost square shape from a horizontal view.
The above-mentioned lens material resin layer is formed into a microlens by
heating it to be melt.
The followings are illustrative examples of the invention.
EXAMPLE 1
FIG. 1(a) to FIG. 1(f) are a flow chart of cross-sectional views showing
the method of manufacturing a color solid state imaging device of one
embodiment of the invention. In FIG. 1(a) to FIG. 1(f), number 1 is a
semiconductor substrate whereon a solid state imaging element is formed.
2a and 2b are planarization resin layers of acrylic resin which are 0.2 to
0.8 .mu.m in thickness (0.6 .mu.m in this example). 3 is a shading layer
of methacrylate resin which is 0.1 to 0.5 .mu.m in thickness (in this
example, 0.3 .mu.m). 4 is a yellow layer of methacrylate resin which is
0.2 to 1.0 .mu.m in thickness (in this example, 0.8 .mu.m). 5 is a cyan
layer of methacrylate resin which is 0.2 to 1.0 .mu.m in thickness (in
this example, 0.5 .mu.m). 6 is a magenta layer which is 0.2 to 1.0 .mu.m
in thickness (in this example, 0.3 .mu.m). 7 is a green layer which is 0.4
to 2.0 .mu.m in thickness (in this example, formed with overlapping yellow
layer 4 and cyan layer 5). 8 is a planarization layer of acrylic resin
which is 0.3 to 1.0 .mu.m in thickness (in this example, 0.6 .mu.m). 9 is
a microlens which is 1.5 to 3.0 .mu.m at the thickest part (in this
example, 2.2 .mu.m).
A transparent planarization resin layer 2a of acrylic resin is formed on a
semiconductor substrate 1 whereon a solid state imaging element is formed,
and subsequently, a shading layer 3, and another planarization resin layer
2b are formed (FIG. 1 (a)).
A synthetic resin (methacrylate resin) was prepared and a photosensitizer
of commercially available diazo compound was added to the resin. As the
diazo compound, for example, [Ar--N.sup.+ .tbd.N]X.sup.- (Ar is Aryl
group) was used. On the above-mentioned planarization resin layer 2b, the
layer of the synthetic resin was coated to be 0.2 to 0.8 .mu.m thick by,
for example, a spin coat method. Then, tile synthetic resin was
selectively exposed with a stepper, and developed to form patterns of a
color filter. The pattern is almost a square of 4 to 5 .mu.m from a
horizontal view. Then, the resin with the pattern was dyed to be a cyan
layer 4 (FIG. 1(b)). In this step, ammonium acetate and ethyleneurea
(2-imidazolidone) were added to the aqueous dyestuff solution. The amount
of the additives are described below.
FIG. 2 shows the relation between the photo-absorption rate (.lambda.=620
nm) of the spectrum of the dyed filter and the amount of additives
(ammonium acetate and ethyleneurea). It is clear from the graph that
ammonium acetate alone can promote dyeing, however dyeing is further
promoted by adding ammonium acetate and ethyleneurea simultaneously
because of a multiple effect. When ammonium acetate of 2 wt. % or more was
added, crystals appeared in the dyeing solution and particles increase.
When ethyleneurea of 10 wt. % or more was added, molecules of excessive
dyestuffs penetrate into the filters and can cause cracks in the filters.
To prevent such problems, the additives were added to the aqueous dyestuff
solution in the rate of the following description.
______________________________________
(1) cyan dyestuff (NIPPON KAYAKU Co.,
2 weight parts
Ltd., copper phthlocyanine
dye, trade name: Pc Cyan)
(2) pure water 838 weight parts
(3) ammonium acetate 20 weight parts
(4) ethyleneurea 60 weight parts
______________________________________
The dyeing was carried out at the temperature of 70.degree. C. for 20
minutes.
FIG. 3 shows the spectral characteristics of the filter of 0.7 .mu.m thick
which was formed in the above-mentioned aqueous dyestuff solution. It is
clear from the graph that the preferable spectrum appears even if the
filter is thin.
After being dyed, the dyeing layers were treated in a solution such as
tannic acid aqueous solution and potassium antimonyl-tartrate solution to
fix the dyestuffs and to prevent decoloring and color-mixing (FIG. 1(b)).
Next, a yellow layer 5 was formed by being dyed with the following yellow
dyestuff in the same manner of the above mentioned cyan layer 4 (FIG.
1(c)).
______________________________________
(1) yellow dyestuff (NIPPON KAYAKU
1 weight part
Co., Ltd., azoic dye, trade name: Pc
Yellow)
(2) pure water 999 weight parts
______________________________________
The dyeing was carried out at the temperature of 70.degree. C. for 20
minutes.
A magenta layer 6 was formed in the same manner as mentioned above (FIG.
1(d)).
______________________________________
(1) magenta dyestuff (NIPPON
1 weight part
KAYAKU Co., Ltd.,
xanthene dye, trade name: Pc Magenta)
(2) pure water 999 weight parts
______________________________________
The dyeing was carried out at the temperature of 40.degree. C. for 10
minutes.
A green layer 7 was formed as the overlapping part of the above-mentioned
yellow layer 4 and cyan layer 5.
Subsequently the color filter was coated with a transparent planarization
layer 8 of acrylic resin to flatten the surface of the color filter (FIG.
1(e)). Then microlens 9 was formed by coating lens material of 0.3 to 1.0
.mu.m thick, exposing selectively, developing, and treating with heat
(FIG. 1(f)). As a material for the lens, a resin such as
polyparavinylphenol resin was prepared and dissolved in a solution of
cellosolve acetate solvent. Then the resin was coated to be 2.2 .mu.m
thick when dried. The lenses were formed by irradiating at g line (436 nm)
by masking at 100 mJ/cm.sup.2, removing exposed parts by using organic
alkali developer, and treating with heat of about 150.degree. C. for 5
minutes. Then the polymer was melted to be a hemispherical lens.
In the example, the thickness of the color filter (from the solid state
imaging element to the bottom of the microlens 9) was 4.0 to 4.5 .mu.m.
FIG. 4 shows spectral characteristics of the colors of the color filter of
this example.
The order of the filter forming method of the invention is not necessarily
limited to the above-mentioned illustrative example.
EXAMPLE 2
FIG. 5(a) to FIG. 5(f) are a flow chart of cross-sectional views showing
the method of manufacturing a color solid state imaging device of one
embodiment of the invention. In FIG. 5(a) to 5(f), number 10 is a
semiconductor substrate on which a solid state imaging element is formed.
11a and 11b are planarization resin layers, 12 is a shading layer, 13 is a
red layer, 14 is a blue layer, 15 is a green layer, 16 is a planarization
resin layer, and 17 is a microlens.
A transparent planarization resin layer 11a (the material is e.g. acrylic
resin) is formed on a semiconductor substrate 10 whereon a solid state
imaging element is formed, and a shading layer 12, and a planarization
resin layer 11b are formed thereon successively (FIG. 5(a)).
Photosensitizer of diazo compound was added to synthetic resin to be dyed
(methacrylate resin) in the same manner of Example 1. On the planarization
resin layer 11b, the dyeable material layer of the synthetic resin was
coated to be 0.2 to 0.8 .mu.m thick, for example, by a spin coat method.
Then, the synthetic resin was selectively exposed with a stepper, and
developed to form patterns of a color filter. Then, the resin with the
pattern was dyed to be a red layer 13. In the step, sodium acetate was
added to the aqueous dyestuff solution.
FIG. 6 shows the relation between the photo-absorption rate (.lambda.=400
nm) of the spectrum of the dyed filter and the amount of sodium acetate as
additive. FIG. 7 shows the absorbance of the red filter (.lambda.=400 nm)
when varying amounts of sodium acetate and urea compound (ethyleneurea)
are added. It is clear from the graph that dyeing is promoted by adding
sodium acetate. Dyeing will be further promoted by adding urea compound
(ethyleneurea) along with the sodium acetate. The above-mentioned
materials were added to the; aqueous dyestuff solution in the amounts
shown in the following description.
______________________________________
(1) red dyestuff (NIPPON KAYAKU Co.,
2 weight parts
Ltd., chrome dye, trade name: Pc Red)
(2) pure water 918 weight parts
(3) sodium acetate 20 weight parts
(4) ethyleneurea 60 weight parts
______________________________________
The dyeing was carried out at the temperature of 70.degree. C. for 20
minutes.
FIG. 8 shows the spectral characteristics of the filter of 0.7 .mu.m thick
which was formed in the above-mentioned aqueous dyestuff solution. It is
clear from the graph that the preferable spectrum appears even if the
filter is thin. Some dyestuffs like the red dye of this example often
generate ammonium salt of the dye by adding ammonium acetate. By adding
sodium acetate, the number of particles of 0.3 .mu.m or more in size can
be reduced to 20 or less per 10 ml of the aqueous dyestuff solution.
After being dyed, the dyeing layers were treated in a solution such as
tannic acid aqueous solution and potassium antimonyl-tartrate solution to
fix the dyestuff and to prevent decoloring and color mixing (FIG. 5(b)).
Next, a blue layer 14 was formed by being dyed with the following blue
dyestuff in the same manner of the above mentioned red layer 13 (FIG.
5(c)).
______________________________________
(1) blue dyestuff (NIPPON KAYAKU Co.,
1 weight part
Ltd., triphenylmethane
dye, trade name: Pc Blue)
(2) pure water 999 weight parts
______________________________________
The dyeing was carried out at the temperature of 70.degree. C. for 20
minutes.
Furthermore a green layer 15 was formed in the same manner as mentioned
above (FIG. 5(d)).
______________________________________
(1) green dyestuff (NIPPON KAYAKU
1 weight part
Co., Ltd., copper
phthalocyanine dye, trade name: Pc Green)
(2) pure water 999 weight parts
______________________________________
The dyeing was carried out at the temperature of 70.degree. C. for 20
minutes.
Subsequently, the color filter was coated with a transparent planarization
layer 16 of 0.3 to 1.0 .mu.m thick (the material is e.g. acrylic resin) to
flatten the surface of the color filter (FIG. 5(e)) in the same way as
Example 1. Then microlens 17 was formed by coating lens material, exposing
selectively, developing, and treating with heat in the same manner of
Example 1 (FIG. 5(f)).
In the example, the thickness of the color filter (from the solid state
imaging element to the bottom of the microlens 7) was as thin as 4.0 to
4.5 .mu.m.
FIG. 9 shows spectral characteristics of the colors of the color filter of
this example.
The order of the filter forming method of the invention is not necessarily
limited to the above-mentioned illustrative example. Sodium acetate, which
was added in the process of forming a red layer of the invention, is also
effective for the process of forming a blue layer and/or green layer.
EXAMPLE 3
FIG. 10(a) to FIG. 10(d) are a flow chart of cross-sectional views showing
the method of manufacturing a solid state imaging device of one embodiment
of the invention. In FIG. 10(a) to 10(d), number 18 is a semiconductor
substrate on which a solid state imaging element is formed. 19 is a
planarization resin layer, 20 is a shading layer, 21 is a planarization
resin layer, and 22 is a microlens.
A transparent planarization resin layer 19 (the material is e.g. acrylic
resin) is formed on a semiconductor substrate 18 on which a solid state
imaging element is formed (FIG. 10(a)).
A synthetic resin (methacrylate resin) was prepared and added
photosensitizer of diazo compound. On the planarization resin layer 19,
the dyeable material layer of the synthetic resin was coated to be 0.2 to
0.8 .mu.m thick by, for example, a spincoat method. Then, the synthetic
resin was selectively exposed with a stepper, and developed to form
patterns of a shading layer. Thereafter, the resin with the pattern was
dyed with black dyestuff to be a shading layer 20. 3In the step, potassium
acetate was added to the aqueous dyestuff solution.
FIG. 11 shows the relation between the absorbance (.lambda.=436 nm) of the
spectrum of the dyed filter and the amount of potassium acetate as
additive. FIG. 12 shows absorbance of the black filter (.lambda.=436 nm)
when varying amounts of potassium acetate and urea compound (ethyleneurea)
were added to the dyeing solution. It is clear from the graph that dyeing
will be promoted by adding potassium acetate. It is also clear that dyeing
is further promoted when a urea compound (ethyleneurea) is added along
with the potassium acetate. Thus the above-mentioned material was added to
the aqueous dyestuff solution in the amounts shown in the following
description.
______________________________________
(1) black dyestuff (NIPPON KAYAKU Co.,
2 weight parts
Ltd., chrome dye, trade name:Pc Black)
(2) pure water 978 weight parts
(3) potassium acetate 20 weight parts
______________________________________
The dyeing was carried out at the temperature of 70.degree. C. for 20
minutes.
FIG. 13 shows the spectral characteristics of the filter of 0.6 .mu.m thick
which was formed in the above-mentioned aqueous dyestuff solution. It is
clear from the graph that the preferable spectrum appears even if the
filter is thin.
Some dyestuffs like the black dye of this example often generate ammonium
salt of the dye by adding ammonium acetate. By adding potassium acetate,
number of such particles of 0.3 .mu.m or more in size can be reduced to 20
or less per 10 ml of the aqueous dyestuff solution.
Subsequently, the filter was coated with a transparent planarization layer
21 of 0.3 to 0.5 .mu.m thick (the material is e.g. acrylic resin) to
flatten the surface of the filter (FIG. 10(c)) in the same way as Example
1. Then microlens 22 was formed by coating lens material, exposing
selectively, developing, and treating with heat in the same manner of
Example 1 (FIG. 10(d)).
As illustrated in the Examples 1 to 3 which are described above, this
invention can provide a solid state imaging device with a color filter
which is dyed densely, is flat, thin, and excellent in spectral
characteristics. Moreover, the method of the invention can increases yield
in manufacturing a solid state imaging device, since particles, which are
generated from aggregation of additives such as dyestuffs, decrease.
The invention may be embodied in other forms without departing from the
spirit or essential characteristics thereof. The embodiments disclosed in
this application are to be considered in all respects as illustrative and
not limitative, the scope of the invention is indicated by the appended
claims rather than by the foregoing description, and all changes which
come within the meaning and range of equivalency of the claims are
intended to be embraced therein.
Top